(a) Field of the Invention
The present invention relates to a hydraulic control system for automotive automatic transmissions.
(b) Description of the Related Art
Conventional automatic transmissions used in vehicles include a torque converter, a multi-stage gear shift mechanism connected to the torque converter, and a plurality of friction members actuated by hydraulic pressure for selecting one of the gear stages of the gear shift mechanism, the gear shift mechanism being realized through a planetary gearset. The friction elements are controlled to engaged and disengaged states by a hydraulic control system, which controls pressure generated in an oil pump, to change shift ratios of the planetary gearset.
When designing such an automatic transmission, a design target is first selected, then a design concept that is good in the aspects of performance, endurance, reliability, and productivity is chosen.
When the design concept is selected, an automatic transmission is developed in three sections, a mechanical section, a hydraulic control section, and an electronic control section.
The mechanical section (powertrain) is usually formed of a compound planetary gear set having at least two simple planetary gear sets. The hydraulic control section controlling the mechanical section includes a pressure regulating part for regulating hydraulic pressure generated from a fluid pump, a manual/automatic shift control part for determining a shift mode, a hydraulic control part for controlling hydraulic pressure to improve shift quality and shift responsiveness, a hydraulic pressure distributing part for properly distributing hydraulic pressure to each friction element, and a damper clutch control part for controlling the operation of a damper clutch of a torque converter.
The hydraulic pressure distribution is varied by solenoid valves that are on/off or duty controlled by a transmission control unit. According to the variation of the distribution, the operation of the friction elements are controlled, thereby realizing the shift control.
Such a powertrain and hydraulic control system has been developed in a variety of types by many different automakers.
However, in the conventional automatic transmission, one control mechanism is controlling at least two friction elements, and thus the friction elements cannot be independently controlled. In addition, since the friction elements are directly controlled by primary control pressure from solenoid valves, solenoid valves having a high capacity and a high degree of preciseness are required, increasing manufacturing costs and operation noise.
Therefore, the present invention has been made in an effort to solve the above problems.
It is a first objective of the present invention to provide a hydraulic control system that can make it possible to use small solenoid valves by independently controlling friction elements and employing an indirect control method whereby secondary control pressure is supplied to the friction elements, thereby reducing manufacturing costs as well as operation noise and vibration.
It is a second objective of the present invention to provide a hydraulic control system that can maintain optimal hydraulic pressure by employing a line pressure regulating solenoid valve, thereby improving the fuel consumption ratio.
It is a third objective of the present invention to provided a hydraulic control system that can minimize shift shock during a manual shifting operation while reducing vibration and fuel consumption ratio by realizing a neutral control in a stop state during driving.
To achieve the above objectives, the present invention provides a hydraulic control system for an automotive automatic transmissions comprising:
a pressure regulator for regulating hydraulic pressure generated by a fluid pump;
a pressure reducer having a reducing valve for reducing hydraulic pressure regulated by the pressure regulator;
a shift controller having a manual valve cooperating with a shift selector lever and connected to a plurality of range pressure lines;
a pressure controller comprising first, second and third solenoid valves for controlling control pressure reduced by the reducing valve, and first, second and third pressure control valves for controlling hydraulic pressure supplied from the manual valve, the first, second and third pressure control valves being independently controlled by control pressure supplied from the first, second and third solenoid valves, respectively;
a switching controller comprising a first switch valve for supplying hydraulic pressure from the first pressure control valve to one of first and second switching lines and a second switch valve for supplying hydraulic pressure from the third pressure control valve and the manual valve to first and second friction elements;
a fail-safer comprising a first fail-safe valve for supplying hydraulic pressure from the first switch valve and the manual valve to a friction element operated in low L and reverse R ranges, and a second fail-safe valve for supplying hydraulic pressure from the second pressure control valve to a friction element operated in second and fourth speeds; and
an N-R controller comprising an N-R control valve for supplying reverse pressure to a friction element operated in only a reverse R range.
The hydraulic control system may further comprise a fourth solenoid valve disposed between the reducing valve and the regulator valve.
The manual valve communicates with a line pressure line for receiving line pressure from the regulator valve, an N-D range pressure line connected to the first pressure control valve and a second fail-safe valve in neutral N and drive D ranges, a D range pressure line connected to the second pressure control valve, the first switch valve, the third pressure control valve, and the second switch valve in the drive D range, an L range pressure line connected to the first switch valve in the low L range, and an R range pressure line connected to the regulator valve, the second fail-safe valve, and the N-R control valve.
The first pressure control valve is provided with a first port for receiving reduced pressure from the reducing valve, a second port for receiving hydraulic pressure from the manual valve, a third port for supplying the hydraulic pressure fed through the second port to the first switch valve, and a fourth port for receiving control pressure from the first solenoid valve, the ports of the first pressure control valve being controlled by a valve spool installed in a valve body, the valve spool comprising a first land on which the hydraulic pressure fed through the first port acts, a second land on which the hydraulic pressure fed through the first port acts to open and close the second port, and a third land for selectively communicating the second port with the third port together with the second land, an elastic member being disposed between the valve body and the third land to bias the valve spool.
The second pressure control valve is provided with a first port for receiving the reduced pressure from the reducing valve, a second port for receiving hydraulic pressure from the manual valve, a third port for supplying the hydraulic pressure fed through the second port to the second fail-safe valve, and a fourth port for receiving control pressure from the second solenoid valve, the ports of the second pressure control valve being controlled by a valve spool installed in a valve body, the valve spool comprising a first land on which hydraulic pressure fed through the first port acts, a second land on which hydraulic pressure fed through the first port acts to selectively open and close the second port, and a third land for selectively communicating the second port with the third port together with the second land, an elastic member being disposed between the third land and the valve body to bias the valve spool.
The third pressure control valve is provided with a first port for receiving reduced pressure from the reducing valve, a second port for receiving hydraulic pressure from the manual valve, a third port for supplying the hydraulic pressure fed through the second port to the second switch valve, and a fourth port for receiving control pressure from the third solenoid valve, the ports of the third pressure control valve being controlled by a valve spool installed in a valve body, the valve spool comprising a first land on which the hydraulic pressure fed through the first port acts, a second land on which the hydraulic pressure fed through the first port acts to selectively open and close the second port, and a third land for selectively communicating the second port with the third port, an elastic member being disposed between the valve body and the third land to bias the valve spool.
The first switch valve is designed to supply N-D range pressure to one of a second clutch and a first brake.
The first switch valve is provided with a first port for receiving N-D range pressure from the manual valve as control pressure, a second port for receiving L range pressure from the manual valve as control pressure, a third port for receiving control pressure from the on/off solenoid valve, a fourth port for receiving hydraulic pressure from the first pressure control valve, a fifth port for supplying hydraulic pressure fed through the fourth port to the second clutch and the first and second fail-safe valves as control pressure, a sixth port for supplying hydraulic pressure fed through the fourth port to the first fail-safe valve, and first and second exhaust ports for exhausting hydraulic pressure returning to the fifth and sixth ports, the ports of the first switch valve being controlled by a valve spool installed in the valve body, the valve spool comprising a first land on which control pressure fed through the first port acts, a second land for selectively communicating the fourth port with the sixth port, a third land for selectively communicating the fourth port with the fifth port, a forth land on which control pressure fed through the third port acts, and a fifth land on which control pressure fed through the second port acts.
The first switch valve is controlled by control pressure fed through the first port and supplies operating pressure from the pressure control valve to a second clutch in first, second, third and fourth speeds; and
is controlled by pressure control pressure fed through the second and third ports in the low L range and supplies operating pressure from the first pressure control valve to the first brake, thereby preventing hydraulic pressure from being supplied to both the second clutch and the first brake simultaneously.
The second switch valve:
supplies hydraulic pressure from the third pressure control valve to a fourth clutch valve and supplied N-D range pressure from the manual valve to a first clutch in second, third and fourth speeds;
is controlled by an on/off solenoid valve and supplies line pressure to the fourth clutch in neutral N, parking P and reverse R ranges; and
supplies D range pressure from the manual valve to the fourth clutch and at the same time hydraulic pressure from the first pressure control valve to the first clutch.
The second switch valve is provided with a first port for receiving D range pressure from the manual valve, a second port for receiving control pressure from the on/off solenoid valve, a third port for receiving hydraulic pressure from the third pressure control valve, a fourth port for receiving line pressure, a fifth port for supplying the hydraulic pressure fed through the third port to the first clutch, a sixth port for supplying the hydraulic pressure fed through the first port to the first clutch, a seventh port for supplying hydraulic pressure fed through the fourth port the fourth clutch, an eighth port for supplying hydraulic pressure fed through the third port to the fourth clutch, and first and second exhaust ports for exhausting hydraulic pressure returning to the fifth, sixth, seventh, and eighth ports, the ports of the second switch valve being controlled by a valve spool installed in the valve body, the valve spool comprising first and second lands for selectively communicating the first port with the sixth port according to control pressure fed through the first port, a third land for selectively communicating the third port with the fifth port, a fourth land for selectively communicating the third port with the eighth port, a fifth land for selectively communicating the fourth port with the seventh port, and a sixth land on which the control pressure fed through the second port acts.
Fluid lines respectively connected to the fifth and sixth ports communicate with the first clutch through a first shuttle valve, and a first branch line branched off from a downstream side of the first shuttle valve is connected to a second branch line branched off from an upstream side of the first port via the first check valve which prevents fluid from flowing in a reverse direction.
A third branch line branched off from the second branch line is connected to the first and second fail-safe valves through a second check valve.
Fluid lines extended from the seventh and eighth ports are connected to the fourth clutch through a second shuttle valve, and a branch line branched off from a downstream side of the second shuttle valve is connected to the second fail-safe valve to supply control pressure to the second fail-safe valve.
The first fail-safe valve:
is controlled by the pressure and supplies hydraulic pressure from the first switch valve to the first brake in neutral N, parking P and low L ranges; and
supplies R range pressure from a reverse R range line to the first brake.
The first fail-safe valve is provided with a first port for receiving hydraulic pressure being directed to the second clutch as control pressure, a second port for receiving hydraulic pressure being directed to the second brake as control pressure, a third port for receiving line pressure as control pressure, a fourth port for receiving hydraulic pressure from the R range pressure line and the first switch valve through a third shuttle valve, and a fifth port for supplying hydraulic pressure fed through the fourth port to the third clutch, the ports of the first fail-safe valve being controlled by a valve spool installed in the valve body, the valve spool comprising a first land on which control pressure fed through the first port acts, a second land on which control pressure fed through the second port acts, a third land for selectively communicating the fourth port with the fifth port, a fourth land for selectively communicating the fourth port with the fifth port together with the third land, and a fifth land on which control pressure fed through the third port acts.
The second fail-safe valve is designed to supply hydraulic pressure from the second pressure control valve to the second brake in second and fourth speeds.
The second fail-safe valve is provided with a first port for receiving R range pressure as control pressure, a second port for receiving part of hydraulic pressure being directed to the fourth brake as control pressure, a third port for receiving part of hydraulic pressure being directed to the second clutch as control pressure, a fourth port for receiving N-D range pressure as control pressure, and a fifth port for receiving hydraulic pressure from the second pressure control valve, and a sixth port supplying hydraulic pressure fed through the fifth port to the second brake, the ports of the second fail-safe valve being controlled by a valve spool installed in the valve body, the valve spool comprising a first land on which control pressure fed through the first port acts, a second land on which control pressure fed through the second port acts, a third land on which control pressure fed through the third port acts, a fourth land for selectively communicating the fifth port with the sixth port, a fifth land for selectively communicating the fifth port with the sixth port together with the fourth land, and a sixth land on which control pressure fed through the fourth port acts.
The N-R control valve is controlled by control pressure fed from the second solenoid valve, and supplies hydraulic pressure from the manual valve to the third clutch in a reverse R range.
The N-R control valve is provided with a first port for receiving control pressure of the second solenoid valve, a second port connected to an R range pressure line, and a third port for supplying hydraulic pressure fed through the second port to the third clutch, the ports of the N-R control valve being controlled by a valve spool installed in the valve body, the valve spool comprising a first land on which hydraulic pressure fed through the first port acts, and a second land for selectively opening and closing the second and third ports, an elastic member being disposed between the second land and the valve body to bias the valve spool.
A branch line branched off from a downstream side of the third port is connected to the R range pressure line via a third check valve.